Why is `pbkdf-parallel` clamped at `4`?

It was at 8/4, since always (2017, 0abf57be / 5fc79f56),

I've looked in docs/etc, and i don't see it spelled out anywhere as to why. It does not appear to be an angorithmic limit, since keepassxc happily allows much higher thread count for Argon2.

Sure, much like with iter-time and memory, it's really easy to shoot oneself into the foot. but while a hard limit of 8 may have made some sense in ~2015 (Ryzen only appeared in ~2017), nowadays it seems to be a handicap given that 32 thread CPU's are rather mainstream. Is that limit really needed?

Same question for memory limit, but at least that is at 4 gigs...